This invention relates to an alternating current generator used with the generator mounted in a vehicle and particularly, terminal treatment of a lead conductor of a stator coil.
Typically, a three-phase alternating current generator having a rotor of launder type is used in a generator mounted in a vehicle. In such an alternating current generator, whose configuration is disclosed in, for example, the Unexamined Japanese Patent Application Publication No. Hei 4-168952, a three-phase stator coil is wound and inserted into a stator core in the stator side, and the stator coil has a lead conductor, and a metal terminal is mounted in the end of the lead conductor and is connected and fixed in a commutator of three-phase full wave type provided in a bracket. A copper wire having a high heat-resistant insulating film such as a polyamide-imide electric wire is used as the stator coil and the lead conductor is provided so that this copper wire (single core copper wire) extends from the stator coil. The metal terminal formed of copper group metals is bonded to the lead conductor by soldering, combination of caulking with soldering, or fusing, and is fixed in the commutator by screws.
The alternating current generator for vehicle is mounted in an engine frame within an engine room of a vehicle, and atmospheric temperature is high and applied vibration is also large. In particular, the temperature of the stator coil is increased to about 200xc2x0 C. which is the heat-resistant limit of the high heat-resistant insulating film in addition to the high atmospheric temperature at heavy load, and when the soldering described above is used in bonding between the lead conductor of the stator coil and the metal terminal, heat deterioration develops and the increase in bonding resistance of a bonded portion may result in breaking of wire. Because of this, a high-temperature solder with high Pb (lead) content must be used, but there were problems that the high-temperature solder with high Pb content causes deterioration of working atmosphere and reliability is reduced due to very bad workability.
Also, bonding by the fusing has the disadvantages that a form of the bonded portion is not stable and fatigue fracture due to vibration during use tends to occur since the bonding is fused by applying pressure, and both strength and electrical conduction became unstable in case that the bonded portion is dependent on caulking. Further, it was contemplated that the copper wire of the lead conductor is welded to the metal terminal as an alternative to these bonding methods. But in this case, while hardening or crack of the copper wire due to weld temperature occurs, intergranular crack is caused by occurrence of water vapor associated with reduction of oxides included in the metal terminal or the lead conductor and blowholes occur within a molten conductor, with the result that a decrease in resistance to vibration or an increase in electrical resistance of the bonded portion was caused and reliability was greatly influenced.
The invention is implemented to solve such problems, and it is an object of the invention to obtain an alternating current generator for vehicle with high reliability in which a bonded portion of the end of a lead conductor of a stator coil does not deteriorate to temperature or vibration.
An alternating current generator for vehicle according to the invention comprises a stator including a stator core and a polyphase stator coil having a lead conductor wound and inserted into this stator core, a rotor in which rotor cores for forming magnetic poles are fixed in a rotating shaft, a front bracket and a rear bracket for holding the stator and rotatably supporting the rotor, and a commutator which is mounted in this rear bracket and to which a metal terminal bonded to the lead conductor of the stator coil is connected, and it is configured so that bonding between the lead conductor and the metal terminal is fixed by caulking with bonding pieces provided in the metal terminal embracing the end of the lead conductor from both sides and spacing between the bonding pieces embracing from both of these sides is bonded and fixed by arc welding.
Also, it is configured so that fixation by welding of the spacing between the bonding pieces is performed in a part of the longitudinal direction of the spacing between the bonding pieces. Further, it is configured so that fixation by welding of the spacing between the bonding pieces is welded including a part of the lead conductor. Furthermore, it is configured so that a notch as the lead conductor is partially exposed in a state fixed by caulking is provided in the tip side of the lead conductor of the bonding pieces and spacing between the bonding pieces is welded and fixed in the vicinity of this notch.
Also, an applied pressure at the time of caulking is set so that a residual rate of a sectional area of the lead conductor becomes 70 to 80% in the fixation by caulking of the lead conductor by the bonding pieces. Further, it is configured so that oxygen free copper is used in at least one of the lead conductor and the metal terminal. Furthermore, it is configured so that the metal terminal is formed of a material with a hardness higher than that of the lead conductor. Also, it is configured so that solder coating is applied to a bonded portion by welding. Further, it is configured so that the lead conductor swaged and fixed by the bonding pieces of the metal terminal consists of a plurality of lead conductors.